Closures for packages



May 2, 1967 J. LASOFF GLOSURES FOR PACKAGES Original Filed Jan. 31, 1962 HIHI FIG.

INVENTOR FIG. 2

JACOB LASOFF ATTORNEY.

- of ground United States Patent 3,317,119 CLOSURES FOR PACKAGES Jacob Lasoilf, Lexington, Mass., assignor to W. R. Grace & C0., Cambridge, Mass., a corporation of Connecticut Original application Jan. 31, 1962, Ser. No. 170,076, now

Patent No. 3,197,938, dated Aug. 3, 1965. Divided and this application May 7, 1965, Ser. No. 464,260

3 Claims. (Cl. 229-62) This application is a division of our prior copending application, Ser. No. 170,076, filed Jan. 31, 1962, now U.S. Patent Number 3,197,938, issued Aug. 3, 1965.

This invention relates to closures for packages made of plastic film, and particularly to those closures known as a twisted seal. Twisted seals are commonly used to close the bags which are used to enclose poultry, sausage meat, hamburg, etc., and are formed by gathering the end of the bag and then twisting it tightly. Commonly, the twist is maintained by a metal clip which surrounds the neck and is tightly compressed against the twisted plastic.

When properly made, twisted seals are truly hermetic, but the presence of metal, particularly in bulk packages meat, is sometimes undesirable. It has not been heretofore practicable to fuse the plastic in the twisted seal so that a heat seal can be made. The thin film covering the product immediately behind the seal usually softens and tears before the considerable mass of the plastic seal can be fused. For this reason, clips are commonly used. The present invention forms a plastic retaining ring for the twisted seal which is so firmly attached to the film that there is no danger of a clip coming loose and separating from the plastic bag. It may be coded either by indicia or color and is quickly made and inexpensive.

This invention has been developed as a component of high speed vacuumizing and bag closing machines described in my U.S. Patent 3,197,938. As the description proceeds, however, it will become obvious that the apparatus may be used separately and that plastic retainers for neck seals can be formed as a subsequent operation :and independently of the vacuumizing and twist sealing apparatus. It should also be understood that the IWOld bag has been used as a convenient term, and not only includes true bags such as those used to enclose poultry, but rolled sheet wrappings which are commonly used to enclose sausage and ground meat and are closed with a twisted seal at each end of the package.

In high speed vacuum twist sealing machines the product, say a turkey, after having been placed in the bag, is placed on a table which permits limited horizontal motion. The neck of the bag is gathered about a hollow horizontal spindle through which air present in the bag is sucked out. When a sufiicient degree of vacuum has been attained, the spindle begins to rotate, twisting the neck of the bag into a tight, rope-like twist. At the same time, the table moves slightly toward the end of the spindle to compensate for the shortening which occurs in the neck during the twisting operation.

Such a machine is exemplified by United States Patent No. 2,733,564, issued Feb. 7, 1956, to Arthur G. Russell et al. As the preferred example, the present invention will be described as used in connection with machines of this type and in substitution for the metal clip applying mechanisms which are shown in the Russell et al. patent.

In the accompanying drawings:

FIGURE 1 is a partial front elevation of a suitable machine for preparing the package of this invention illustrating the relative position of the head, spindle, and the product;

3,317,119 Patented May 2, 1967 "ice FIGURE 2 shows the completed seal retainer in place on a twisted neck. A machine suitable for preparing the package of this invention comprises a work table 10 supported upon a cabinet base 11 in which is housed a driving motor and the vacuum pump (not shown). The machine is provided with a head stock 12 which as in the Russell machine contains a vacuum hearing" which allows air to be drawn through the hollow spindle 13 which is rotated by an operative connection with the motor. Sliding table 14 moves longitudinally in ways 15 which are fixed to the work table 10.

The product 16 (here represented as a turkey already placed in a plastic bag) is placed on the sliding table 14. The neck of the bag is drawn over the nozzle 17 of spindle 13 which is then rotated for a few turns twisting the neck of the bag into a tight rope-like neck 18. When these operations are complete, a plastic retaining ring is molded about the twisted neck 18 of the bag by any suitable apparatus such as described in U.S. Patent Number 3,197,938 in lieu thereof and incorporated herein by reference.

The means employed in U.S. 3,197,938 comprises a small injection molding having a molding chamber adapted to completely enclose the twisted bag neck when rotatable die 31 is in the closed position. The die tightly compresses the neck when the die is closed to prevent flash leakage along the neck and folds. The device also includes a head having a small pellet receiver 43 which discharges its contents by gravity into an injection molding device where the pellets are melted. After the twisted neck has been inserted in the molding chamber and the die 31 closed, the melt is injected into the chamber to form the molded ring 72. The ring is then cooled, the die 31 opened and the sealed bag neck removed.

The seal which is formed, shown in FIGURE 2, consists of a plastic ring 72 molded into and conforming internally to the external configuration of the twisted neck 18. If a ring is broken open, it will be seen that some of its substance has flowed into the folds and twists of the neck material. This intermolding of the ring with the neck material grips the twisted seal so tightly that untwisting is impossible. Ring 72 cannot be removed from the twist. Opening the package requires that the bag be cut or torn. Upon cooling, the plastic ring shrinks further, tightening the twisted neck.

If the bag is made of heat-shrinking material, as are most poultry bags, a drawing backwards and a tightening of the seal occurs due to the heat derived from the molten plastic of ring 72. Although metal securing clips are commercially satisfactory, the present invention forms an even tighter hermetic seal when heat shrinking film is used.

A considerable choice of material for the ring 72 exists. Among suitable materials may be mentioned polyethylene, cellulose acetate, high impact polystyrene, and other wellknown injection molding thermoplastics. High density polyethylene has given superior results and because of its low cost and ability to withstand abuse is the preferred material.

In addition to the advantage that no metal clip is used, a considerable advantage of a plastic ring is the coding which becomes possible. Marking may be engraved in the die and the material which forms the ring may the colored so that particular products, weights, or grades may be quickly identified by the color or marking which is used.

What is claimed is:

1. A hermetically sealed package comprising an object completely enclosed in an enveloping film of thermoplastic material, said film extending beyond the object on at least one portion of the package and being twisted into an elongated neck, said neck being restrained by a molded plastic retainer ring completely and tightly encircling 5 30111690 References Cited by the Examiner UNITED STATES PATENTS 12/1953 Eichler 229-65 X 12/1961 Gabuzda 229-62 FOREIGN PATENTS 3/1959 Canada. 12/ 1953 Great Britain.

10 JOSEPH R. LECLAIR, Primary Examiner.

DAVID M. BOCKENEK, Examiner. 

1. A HERMETICALLY SEALED PACKAGE COMPRISING AN OBJECT COMPLETELY ENCLOSED IN AN ENVELOPING FILM OF THERMOPLASTIC MATERIAL, SAID FILM EXTENDING BEYOND THE OBJECT ON AT LEAST ONE PORTION OF THE PACKAGE AND BEING TWISTED INTO AN ELONGATED NECK, SAID NECK BEING RESTRAINED BY A MOLDED PLASTIC RETAINER RING COMPLETELY AND TIGHTLY ENCIRCLING SAID NECK, THE INTERNAL SURFACE OF SAID RING CONFORMING TO THE EXTERNAL CONFIGURATION OF THE TWISTED NECK AND INTERPENETRATING THE FOLDS OF SAID TWISTED NECK. 